The multitude of electrical and electronic devices in common use today, from cellular telephones to computers to lighting systems, all depend on a steady supply of electrical energy. Such a supply is not an issue when a device is connected to a constant source of electrical energy via a land electrical power line, for example through a power receptacle. However, portable electrical devices or devices located in areas without electrical power lines (for example marine craft, space vehicles, non-powered air vehicles, etc.), must acquire their electrical energy from batteries or through other electrical energy sources (solar panels, hydro-power generators, fuel cells, wind-power generators, etc.). Examples of portable electrical devices include, but are not limited to: miniature electrical devices (such as: an implantable cardiac device (pacemaker, defibrillator), a chronograph, a miniature surveillance device (remote mini-camera, concealable tracking device, motion detecting device), an electronic tag (RF, etc.), and small to medium electrical devices (such as a personal electronic device (a mobile telephone, a radio, a television, a personal digital assistant (PDA), a media player and/or recorder, a video or photo camera, a game console, binoculars, night vision goggles, a portable computer (notebook, laptop, or tablet computer), a portable data acquisition device (i.e. RF or barcode scanner), a portable medical diagnostic or treatment delivery device (e.g. blood pressure monitor, electrocardiogram machine, defibrillator, drug pump, etc.), a surveillance device (remote camera, tracking device, motion detecting device), a weapon or weapon accessory with electrical or electronic capabilities (e.g., a camera and/or scope on a rifle, a taser, a laser targeting sight, or a laser targeter), toys, and robotic devices.
In the past several decades, the proliferation of portable electrically powered devices, such as illustrated above, has created a great need for efficient and miniaturized sources of electrical energy. Utilization of ordinary disposable batteries (alkaline, etc.) greatly increases the cost of operation of such devices, especially because many electrical devices (for example, digital cameras) draw electrical energy in such a way as to quickly exhaust a conventional battery. In addition, users find frequent replacement of batteries and carrying spare batteries very inconvenient.
Therefore, in recent years, rechargeable batteries (such as Metal Oxide, NiCad, etc.) are typically used. Nevertheless, while rechargeable batteries, especially the latest currently available models, offer longer operational time and lower cost of operation, they are still finite sources of electrical energy and must be recharged relatively often. This is problematic for high utilization devices, such as PDAs, media recorders/players, portable telephones and laptop computers. Furthermore, because recharging involves connecting the device or its battery to a land power line, the recharging process limits the user's mobility. For that reason, many users are forced to carry one or more additional spare rechargeable batteries for their devices, and in some cases a recharging device or adapter (for example, when traveling). Other portable electrical devices, such as flashlights and the like, can also benefit from efficient long-lasting sources of electrical energy and sometimes rely on rechargeable batteries to lower operational costs with similar disadvantages as previously described electrical devices.
In some cases, where the use of rechargeable batteries is not practical or possible (such as in pacemakers and wrist chronographs), special extended duration non-rechargeable batteries (for-example, lithium batteries) are used. While such batteries may be replaceable, in the case of implantable medical devices, surgical intervention is necessary to extract the device. Furthermore, to maintain sterility, batteries in implantable medical devices are never changed, even when the device is extracted. Rather, the implantable device is disposed of, and replaced with a new one.
In addition, certain critical function devices, such as medical devices (e.g. pacemakers, drug pumps, etc.), environmental hazard (chemical, radiation, and/or biological) suits, or space vehicles (satellites, space shuttle, planetary robotic vehicles, extra-vehicular activity (EVA) suits, etc.) often require very reliable and sometimes redundant sources of electrical energy.
All types of batteries (rechargeable and otherwise), suffer from two additional disadvantages. First, most batteries utilize non-recyclable toxic and/or environmentally polluting materials in their construction, making disposal of used batteries a environmental danger. Second, all batteries generate heat during operation, requiring cooling in sensitive electronic equipment (such as in portable computers). The heat generation from batteries is a particular danger in military devices where the heat signature exposes the carrier of the device to enemy infra-red or other heat sensing surveillance or targeting equipment. This is particularly true of fuel cell batteries often used in military applications due to their inherent high capacity. For example, fuel cell batteries have operating temperatures that often exceed 100 degrees Fahrenheit.
To address these challenges, there has been some development in the field of portable generation of electrical energy that may be utilized to power an electrical device, to recharge the rechargeable batteries in a device, or both. Typically, previously known portable electrical generators involve some form of transduction of mechanical energy into electrical energy by implementation of the Faraday's Principle of Induction, in which motion of the generator (such as shaking or vibration) is translated into rotational movement of a coil and a magnetic rotor, at least partially disposed within the coil, relative to one another. This relative motion generates electrical energy at the coil caused by the rotation of the magnetic field of the rotor. The generated electrical energy is then typically rectified by a capacitor circuit to convert it to direct current (DC) power. The electrical energy may be used directly, stored, or routed to a rechargeable battery.
Some previously known kinetic-power generation (hereinafter “KEPG”) systems are configured to derive electrical energy from relative linear motion of the coil and rotor—these systems require vigorous shaking motion to generate electrical energy and offer some advantages in that the desired electrical energy is relatively quickly generated. However, this approach requires direct dedicated action by the user to generate the energy that is difficult and impractical to sustain. Also, only small amounts of electrical energy may be practically generated in this manner. Furthermore, vigorous motion of certain electronic devices, such as laptop computers or medical devices, is highly undesirable.
In many previously known KEPG systems, an attempt has been made to utilize ordinary motion (such as walking, moving a limb, floating on waves in the water, etc.) to generate electrical energy in a manner that is transparent to the user. In most of these systems, translation of ordinary motion has been accomplished by utilizing an oscillating weight to convert relatively linear motion of the KEPG system into rotary motion of the rotor relative to the coil via a mechanical motion converter, such as a gear train. However, except for limited use in wrist chronographs, these systems have failed to achieve commercial success for a number of reasons. First, miniaturized KEPG systems must overcome a significant challenge in that the oscillating weight responsible for translating vibrational or semi-linear motion into desirable rotary motion must be of a very small size which makes it light, and thus limits its acceleration and range of angular motion during continuous operation, resulting in a decrease overall system performance proportional to the oscillating weight's size. Accordingly, previously known KEPG systems cannot provide sufficient amounts of electrical energy for tiny, small or medium electrical devices to justify their use.
In addition, due to the construction and operational characteristics of the previously known oscillating weights, the motion threshold—i.e. the minimum mechanical disturbance (in terms of the magnitude and directionality of inertial forces) that must be applied to the electrical device and transferred to the oscillating weight, to cause the weight to achieve sufficient repetitive angular motion to cause rotation of the rotor—is typically very high. Thus, to exceed the motion threshold, a device equipped with a previously known KEPG system must be subjected to significant mechanical disturbances to derive a meaningful benefit from the KEPG system. This is one of the reasons why the only commercially successful use of oscillating weight-based KEPG systems has been in wrist chronographs—the routine motion of an average person's wrist during typical daily activities continually provides a sufficient amount of mechanical disturbances of a magnitude that meets or exceeds a typical wrist chronograph-based KEPG system's motion threshold.
The challenge of the high motion threshold in previously known KEPG systems have also stymied their utilization in applications where the size of a KEPG system is less of an issue—for example, in marine power (buoy, marine craft, etc.) applications. In marine applications, moderately calm to slightly choppy waters—the most common marine conditions in the majority of the bodies of water, will typically fail to produce sufficient mechanical disturbances to the marine device or craft to exceed the motion threshold of most KEPG systems.
Thus, it would be desirable to provide an apparatus and method for efficiently generating electrical energy from motion, including routine motion. It would also be desirable to provide an apparatus and method for efficiently generating electrical energy utilizing an oscillating weight with superior acceleration and momentum characteristics relative to its size, to enable advantageous KEPG system utilization regardless of its size. It would further be desirable to provide an apparatus and method for generating electrical energy having a lower motion threshold than previously known KEPG systems.